Internal combustion engine piston and oil ring for same



Dec. 16, 1958 H. M. SEUBERT, JR 2,864,660

INTERNAL COMBUSTION ENGINE PISTON AND OIL RING FOR SAME Filed April 11,1956 l0 INVENTOR. HARRY M. SEUBERT JR.

ATTORNEY Unite tates Pater INTERNAL COMBUSTION ENGINE PISTON AND 01LRING FOR SAME Harry M. Seubert, .lr., Toledo, Ohio Application April 11,1956, Serial No. 577,608

Claims. (Cl. 309-45) This invention relates to internal combustionengines, but more particularly to pistons and oil rings used in internalcombustion engines.

There are two major problems encountered by designers of pistons forinternal combustion engines. In the first place the differential inthermo expansion between the piston head and the piston skirt due totemperature differential that exists in these two areas during engineoperation, constitutes one of these problems. The other problem isconcerned with the differential in thermo expansion between the pistonpin bosses and the piston wall 90 from these bosses due to thedifference in the amount of piston mass located in each of these areas.

The endeavors to cope with these problems have involved the tapering ofthe piston so that the piston head is smaller in diameter than the upperskirt of the piston. Additionally a metallic band has been cast in thepiston at the highest thermo expansion point, the metal being of a lowercoefi'icient of expansion and supposedly decreasing the pistons rate ofexpansion in this particular area. These efforts have been directed toovercome the problem of the differential in thermo expansion as abovementioned.

The eflforts to cope with the second problem above mentioned, i. e. thedifferential in thermo expansion between the piston pin bosses and thepiston wall, has resulted in slotting the piston skirt in horizontal andvertical planes and also the proportioning the mass of the piston toachieve the optimum expansion characteristics.

Additional problems are faced by the unequal piston skirt wear and pooroil control and in an endeavor. to solve these problems, the pistonskirt has been cam ground and the skirt has been made of a flexiblenature. The type of cam profile employed is dependent upon the nature ofthe piston design and engine application and is quite a costlyoperation.

The important item in all of these endeavors is to maintain a clearancebetween the piston and the cylinder wall at all engine speed-loadconditions. Too much clearance causes excessive piston slap at lowspeeds and too little clearance results in piston scufiing and seizing.

It is a desideratum to provide a practical and economical solution tothe above problems, eliminating all costly efforts and produce a pistondesigned with sufficient clearance to satisfy the high speed-loaddemands and employ a low friction piston oil ring in the skirt area ofthe piston, properly preloaded so as to be in contact with the cylinderwall at the lowest operational temperature expected for engineoperation.

An object is to overcome the above difliculties and to produce a pistonand oil ring assembly which satisfactorily copes with the severalproblems and which is efficient and economical.

Another object is to produce a new and improved piston structureequipped with a rotating oil ring having the unique features ofconstruction and operation hereinafter described.

Other objects and advantages of the invention will hereinafter appear,and for purposes of illustration but not of limitation, an embodiment ofthe invention is shown on the accompanying drawing in which Figure 1 isa somewhat diagrammatic view partly in elevation and partly in verticalsection of a piston disposed within an engine cylinder and equipped withthe oil ring in accordance with this invention;

Figure 2 is an enlarged fragmentary transverse section substantiallyalong the line 22 of Figure 1;

Figures 3, 4 and 5 are diagrammatic views showing different positions ofthe rotating oil ring in different positions of the piston;

Figure 6 is a diagrammatic view showing a portion of the piston andadjacent cylinder wall and illustrating by broken lines operationalcharacteristics of the rotating oil ring;

Figure 7 isa view somewhat similar to Figure 6 showing the elasticdeformation of the oil ring due to piston side thrust load, and

Figure 8 is a diagrammatic view similar to Figure 6 illustrating the oilmetering action of the rotating oil ring.

The illustrated embodiment of the invention comprises a piston 10 havinga head 11 at the upper end thereof equipped with the usual rings 12.Depending from the head 11 is a separate segmental skirt 13 suitablyfixed to the head by an integral connection 14 providing bosses toreceive the connecting rod wrist pin 15. The piston is reciprocablewithin an engine cylinder 16.

Formed in the outer side of the piston skirt 13 is a cylindrical channel17 which is long tudinally elongate and the inner wall of which isparallel to the Wall of the cylinder receiving the piston. Disposedwithin and embracing the channel 17 is an endles garter-type oil ring 13which is of an helical wire of metal or other suitable material. Thediameter of the wire forming the continuous helix and the spacingbetween adjacent convolutions determine the amount of oil which will bemetered in the operation of the piston and also the amount of pistonside thrust which the oil ring can absorb. For greater load absorbingproperties, a larger wire diameter is necessary thereby increasing thespace between the adjacent convolutions and also resulting in anincrease in the quantity of oil which will be metered. Preferably thewire form ng the oil ring is round in cross section in order tofacilitate the rotating action of the ring in the operation of thepiston.

Figures 3, 4 and 5 show different positions of the rotating oil ring 18during the reciprocatory movement of the piston 10. Thus it will beobserved that the oil ring moves from one end to the other of thechannel 17 and during such movement rotates and as indicated on Figure 8in which the arrow 19 indicates the direction of piston movement, theoil ring moving in the direction of the arrow 20 and at the same timerotating. In such rotational movement, the oil is metered adequately tolubricate the cylinder walls as indicated on Figure 8.

Referring to Figure 6 it will be understood that as the piston moves tothe left of the figure at a given velocity, the oil ring travels in thesame direction but only at one-half the piston velocity. Thus it will bemanifest that although the piston velocity actually varies continuallyduring the stroke, the oil ring 18 also varies its velocity and at thesame rate. In view of the fact that the linear velocity is equal to thedistance divided by time, linear velocity is directly proportional tothe distance traveled. As a consequence the distance traveled by thepiston (the stroke) is twice the distance covered by the oil ring 18. Asindicated on Figure 6, 21 des gnates the distance traveled by the oilring 18 and this distance is always one-half of the piston stroke.

Figure 7 illustrates the elastic deformation of the oil ring 18 whichabsorbs and softens the piston load transferral to the wall of thecylinder, the oil ring being designed to rotate under load. In thisfigure, the broken line 22jillustrates the reduction. of clearance dueto side thrust load on the piston, such thrust being absorbed by the oilring which is resilient and is accordingly deformed but withoutmilitating against its ability to rotate.

In view of the resilience of the oil ring 18, the piston can becylindrical with the same clearance for the skirt 13 as at the head 11,variations in piston diameter along the length of the piston due tothermo distortion and load deformation being absorbed by the oilringshelical deflection, such deflection being illustrated on Figure 2.

It will be manifest that due to the above structure,

cold piston slap is prevented due to the initial prcl-oatb ingimpartedto the oil ring 18. As the engine begins to warm up, the piston beginsto expand unequally in the skirt area. Such unequal expansion iselastically absorbed by the helical deformation of the low-frictionrotating oil ring 18 without ditficulty. At the same time,

the major and minor thrust forces on the wrist pin 15 are cushioned bythe oil ring 18 against the cyl'nder wall, thereby substantiallyreducing wear. Due tothe one-half speed characteristic of the oil ring18 as above pointed out, oil is metered and spread more uniformly overthe cylinder wall a the oil ring rolls up and down in phase with thepiston but only at one-half of its velocity. The normal sliding frictionbetween the cylinder and piston is substantially reduced by a factor ofone-, fifth to one-tenth. Reduction in engine wear and frictionalhorsepower loss is also appreciable due to this structure.

Numerous changes in details of construction, arrangement and choice ofmaterials may be effected without departing from the spirit of theinvention, especially as defined in the appended claims.

What I claim is:

l. A piston assembly for internal combustion engines comprising a pistonhead, a skirt depending from the head and having an inwardly extendingchannel extending around the skirt, and an endless helix of resilientwire-like material embracing said channel and rotatable therein duringits travel from one end of the channel to the other during pistonreciprocation.

2. A piston assembly for internal combustion engines comprising a pistonhead, a skirt depending from the head and having an inwardly extendingchannel extending around the skirt, and an endless helix of resilientwire-like material embracing said channel and rotatable therein duringits travel from one end of the channel to the other during pistonreciprocation, said helix being preloaded when in engagement with thewall of the cylinder receiving the piston.

3. A piston assembly for internal combust on engines comprising a pistonhead, a skirt depending from the head and having an inwardly extendingchannel extending around the skirt, and a preloaded, resilient helixembracing said channel, rotatable and translatorily movable in thechannel during reciprocatory piston movements with the outer portion ofthe helix engageable with the walls of the cylinder receiving thepiston.

4. A piston assembly for internal combustion engines comprising a pistonhead, a skirt depending from the head and having an inwardly extendingchannel extending around the skirt, and an endless helix of resilientwire-like material embracing said channel and rotatable therein duringit travel from one end of the channel to the other during pistonreciprocation, said wire-l ke material being round in cross section andthe spacing of the adjacent convolutions predetermining the amount ofoil to be metered during piston movement.

5. A piston assembly for internal combustion engnes comprising a pistonhead, a skirt depending from the head and having an inwardly extendingchannel extending around the skirt, and an endless helix of resilientwire-like material embracing said channel and rotatable therein duringits travel from one end of the channel to the other during pistonreciprocation, the diameter of the wire-like material beingpredetermined and the spacing of adjacent convolutions predeterminng theamount of oil to be metered during piston operation and the amount ofpiston side thrust to be absorbed.

References Cited in the file of this patent UNITED STATES PATENTS 31,847Young Mar. 26, 1861 207,871 Horton Sept. 10, 1878 391,956 Frager Oct.30, 1888 417,321 Gresham Dec. 17, 1889

